Role of pinnae and head movements in localizing pure tones

Twelve blindfolded subjects localized two different pure tones, randomly pl ayed by eight sound sources in the horizontal plane. Either subjects could get information supplied by their pinnae (external ear) and their head move ments or not, We found that pinnae. as well as head movements, had a marked influence on auditory localization performance with this type of sound. Ef fects of pinnae and head movements seemed to be additive; the absence of on e or the other factor provoked the same loss of localization accuracy and e ven much the same error pattern. Head movement analysis showed that subject s turn their face towards the emitting sound source, except for sources exa ctly in the front or exactly in the rear, which are identified by turning t he head to both sides. The head movement amplitude increased smoothly as th e sound source moved from the anterior to the posterior quadrant.